Final answer:
Both SINEs and non-LTR retrotransposons may have Poly(A) tails at their 3' ends after retrotransposition, even though they are not originally part of the RNA template.
Step-by-step explanation:
The 3' Poly-A Tail is a feature of eukaryotic mRNAs that consists of a string of adenine nucleotides added to the 3' end after transcription is complete. This polyadenylation process involves cleavage of the pre-mRNA downstream of a conserved AAUAAA sequence, followed by the addition of the poly-A tail by poly(A) polymerase. For SINEs (Short Interspersed Nuclear Elements) and non-LTR retrotransposons, the process is a bit different from mRNA polyadenylation but achieves a similar structure at the 3' end.
Non-LTR retrotransposons, which include both LINEs (Long Interspersed Nuclear Elements) and SINEs, do not typically have poly-A tails as part of their original sequence; however, during the process of retrotransposition, a poly-A-like tail can be added. This is because the reverse transcription mechanism used by these elements often results in an adenosine-rich tail at the 3' end of the inserted element. While LINEs encode the necessary enzymes for their retrotransposition, SINEs are non-autonomous and require the presence of LINEs or other autonomous elements to provide the necessary enzymatic activities for their mobilization.
In the context of retrotransposition, both SINEs and non-LTR retrotransposons (like LINEs) may have Poly(A) tails at their 3' ends following their insertion into new genomic locations, even though they are not originally part of the element's RNA template. This tail is akin to the mRNA poly-A tail but is generated in a different manner as part of the retrotransposition process.